Rotary kilns

ABSTRACT

Apparatus for the conversion of a solid material to a gaseous phase by sublimation in which the rate of vaporisation of the solid material is controlled in accordance with the pressure of the gas formed by the conversion. The apparatus finds particular application in the continuous, automatically controlled sublimation of uranium hexafluoride prior to its conversion to uranium dioxide in a gas phase reaction with steam and hydrogen.

United States Patent [191 Gillies et al.

ROTARY KILNS Inventors: George Marshall Gillies, St. Annes;

James Edgar Littlechild, Lytham, both of England United Kingdom AtomicEnergy Authority, London, England Filed: June 1, 1972 Appl. No.: 258,803

Related US. Application Data Division of Ser. No. 132,649, April 9,1970.

[73] Assignee:

US. Cl 62/46, 62/167, 165/39, 165/118 Int. Cl. B6011 l/00 Field ofSearch 165/32, 118, 39; 62/46, 62/49, 167

[56] References Cited UNITED STATES PATENTS 1,456,871 5/1923 Ehrhart..165/32 [451 Sept. 10,1974

1,766,618 6/1930 Feldmeier 165/32 2,125,888 8/1938 Cordrey 62/1672,167,667 8/1939 McMechan... 62/167 2,196,012 4/1940 Gilbert 165/1182,540,293 2/1951 Roswell 165/118 2,996,893 8/1961 Goodenough.. 62/523,371,497 3/1968 Singleton 62/52 3,636,720 1/1972 Krieve 62/49 PrimaryExaminer-Manuel A. Antonakas Assistant Examiner-Daniel J OConnorAttorney, Agent, or Firm-Larson, Taylor & Hinds 1 ABSTRACT Apparatus forthe conversion of a solid material to a .gaseous phase by sublimation inwhich the rate of vaporisation of the solid material is controlled inaccordance with the pressure of the gas formed by the conversion. Theapparatus finds particular application in the continuous, automaticallycontrolled sublimation of uranium hexafiuoride prior to its conversionto uranium dioxide in a gas phase reaction with steam and hydrogen.

4 Claims, 1 Drawing Figure ROTARY KILNS- CROSS-REFERENCES TO RELATEDAPPLICATIONS This application is a division of application Ser. No.132,649 in the names of Gillies et al filed Apr. 9, 1971.

BACKGROUND OF THE INVENTION This invention relates to apparatus for thesolid to gaseous conversion of a material which sublimes.

SUMMARY OF THE INVENTION According to the invention apparatus for thesolid to gaseous conversion of a material which on heating sublimes fromthe solid phase to the gaseous phase'comprises a container for the solidmaterial, the container having a gas outlet, and means for spraying hotwater over the container to cause vaporisation of the material in thecontainer, the rate of supply of hot water to the container andtherefore the rate of vaporisation of the material being controlled inaccordance with the pressure of gas in the container.

In a preferred form of the invention the hot water spray is derived bythe recirculation of water gathered at the base of the container afterspraying over the container, recirculation of the water being by a steamejector which reheats the water, the supply of steam to the ejector andhence the rate of recirculation of the water being controlled inaccordance with the pressure of gas in the container.

A typical industrial process with which the apparatus of the inventionmay be concerned is the continuous conversion of uranium hexafluorideinto uranium diox ide by reaction with steam and hydrogen in a gaseousphase reaction, as described in the specification of our copendingapplication referred to above. In such a process a continuousautomatically controlled supply of gaseous phase uranium hexafluoride isrequired. Normally uranium hexafluoride is supplied for such processesin the solid state in transport containers.

DESCRIPTION OF THE DRAWING An apparatus according to the invention willnowbe described by way of example with reference to the accompanyingdrawing which shows a sectional view of such apparatus.

DESCRIPTION OF THE PREFERRED EMDOBIMENT Referring to the drawing avertically orientated tank 1 is shown having a removable lid 2. Locatedin the tank 1 is a cylindrical transport container 3 containing solidphase uranium hexafluoride. Location for the container 3 in the tank 1is provided by an annular upstand 4 fitted in the base of the tank 1 andby locking bars 5 pivotably attached to the walls of the tank 1immediately below the lid 2 and bearing on the top of the container 3.The top of the container 3 is provided with a lifting attachment 6 and afiller/outlet valve 7. The valve 7 is connected into a line 8 for supplyof gaseous phase uranium hexafluoride to a rotary kiln. Locatedimmediately above the container 3 are two annular pipes 9 and 10, theinternal diameters of which allow the container 3 to be loaded into orremoved from the tank 1 without difficulty. Both of the annular pipes 9and 10 have equidistantly spaced apertures in their inner surfaces whichallow water supplied in the pipes to be sprayed ontothe top of thecontainer 3. The upper annular pipe 9 is connected to a cold watersupply line 11 whilst the lower annular pipe 10 is connected into a hotwater supply line 12 which extends down towards the base of the tank 1where it connects into a steam ejector 13. A pipe l4connects the ejector13 into the bottom of the tank 1. A line 15 supplies steam to theejector 13. The supply of steam to the ejector 13 is controlled by meansof an air controlled valve located in the line 15 which is actuated byan air signal from a pressure transducer located in the line 8. Thus thesteam supply to the ejector 13 is controlled by the pressure of gaseousphase uranium hexafluoride in the line 8'. When the valve 7 is in theopen position the pressure of gaseous phase uranium hexafluoride in theline 8 will be the same as in the cylinder 3.

In operation a container 3 containing uranium hexafluoride in the solidphase is loaded into the tank 1 and located in position by means of theupstand 4 and the locking bars 5. Theline 8 is then connected to thevalve 7 which is then opened. Steam is supplied by the line 15 to theejector 13 causing it to draw water 16 from the base of the tank 1 viathe pipe 14 and pass it mixed with steam up the line 12 into the annularpipe 10 from which it emerges as a hot water spray which is directedonto the top of the container 3. The water from the hot spray runs downthe outside of the container 3 and collects in the base of the tank 1where it is available for recirculation by the ejector 13. The hot waterspray heats the walls of the container 3 and converts the solid phaseuranium hexafluoride contained therein into the gaseous phase whichpasses out of the cylinder 3 via the valve 7 into the line 8.

The pressure of the gaseous uranium hexafluoride controls the amount ofsteam supplied to the ejector l3 and hence controls the volume of hotwater sprayed on to the top of the container 3 from the annular pipe 10.In this way the heat supply to the container 3 and thus the rate ofconversion of the uranium hexafluoride from the solid to the gaseousphase is automatically controlled.

The cold water spray from the annular pipe 9 is used to cool down thecontainer 3 when it is required to stop the conversion of uraniumhexafluoride from the solid to the gaseous phase.

We claim:

1. Apparatus for the solid to gaseous conversion of a solid materialwhich on heating sublimes from the solid phase to the gaseous phase,comprising, in combination, a container in the form of a pressure vesselcontaining a solid sublimable material, said container having a gasoutlet in the upper portion thereof, means for spraying hot water overthe container to cause vapori- Zation of the material in the container,and means for controlling the rate of supply of hot water to thecontainer and therefore the rate of vaporization of the material inaccordance with the pressure of gas in the container.

2. Apparatus as claimed in claim 1 further comprising means forcollecting water at the base of said container after spraying over thecontainer, said means for spraying including means for recirculatingsaid collected water and spraying it over the container, saidrecirculation, means including a steam ejector which recirculates andreheats the water, and said control after spraying over the container,said spraying means including means for recirculating said collectedwater and spraying it over the container, said recirculating meansincluding a steam ejector which recirculates and reheats the water, andsaid control means comprising means responsive to gas pressure in thecontainer for automatically controlling the supply of steam to saidejector in accordance with said gas pressure.

1. Apparatus for the solid to gaseous conversion of a solid materialwhich on heating sublimes from the solid phase to the gaseous phase,comprising, in combination, a container in the form of a pressure vesselcontaining a solid sublimable material, said container having a gasoutlet in the upper portion thereof, means for spraying hot water overthe container to cause vaporization of the material in the container,and means for controlling the rate of supply of hot water to thecontainer and therefore the rate of vaporization of the material inaccordance with the pressure of gas in the container.
 2. Apparatus asclaimed in claim 1 further comprising means for collecting water at thebase of said container after spraying over the container, said means forspraying including means for recirculating said collected water andspraying it over the container, said recirculation, means including asteam ejector which recirculates and reheats the water, and said controlmeans comprising means responsive to gas pressure in the container forautomatically controlling the supply of steam to said ejector inaccordance with said gas pressure.
 3. Apparatus as claimed in claim 1wherein said solid material is solid phase uranium hexafluoride. 4.Apparatus as claimed in claim 3 wherein said container is a transportContainer removably mounted in a tank for collecting water at the baseof said container after spraying over the container, said spraying meansincluding means for recirculating said collected water and spraying itover the container, said recirculating means including a steam ejectorwhich recirculates and reheats the water, and said control meanscomprising means responsive to gas pressure in the container forautomatically controlling the supply of steam to said ejector inaccordance with said gas pressure.